Right-hander Luis Castillo held slumping San Diego to one run on four hits over six innings Saturday night as visiting Cincinnati scored a 4-2 victory at Petco Park.

The Reds have defeated the Padres in each of the first three games of the series. The Padres have lost six in a row, including five straight at Petco Park, to fall to .500 after an 11-5 start.

The only run off winner Castillo (2-1) was a home run by Eric Hosmer leading off the second that temporarily tied the game at 1-1. Castillo struck out nine Padres while issuing one walk. Right-hander Raisel Iglesias struck out the side in the ninth to pick up his fourth save.

The Reds scored three runs (two earned) on six hits and two walks in five innings against left-handed Padres starter Eric Lauer (2-3). Lauer had five strikeouts. Cincinnati’s fourth run came on pinch-hitter Jesse Winkler’s fourth career pinch-hit homer (and sixth of the season) leading off the seventh against reliever Matt Wisler.

Cincinnati scored in the first when leadoff hitter Jose Peraza singled, moved to second on a groundout, stole third and scored when Jose Iglesias lined a two-out drive off the glove of center fielder Wil Myers for a single.

The Reds took a 2-1 lead in the fourth when Scott Schebler, Kyle Farmer and Tucker Barnhart hit consecutive, one-out singles off Lauer. Schebler’s hit was a slow roller to short.

The Reds scored an unearned run in the fifth. Eugenio Suarez drew an inning-opening walk and advanced to third when Lauer’s attempted pick-off throw sailed wide of first baseman Hosmer and down the right field line. Suarez scored on Yasiel Puig’s sacrifice fly to right.

The Padres scored their second run in the bottom of the eighth.

Twenty-year-old rookie shortstop Fernando Tatis Jr. opened the inning with a triple inside the third-base bag — extending his hitting streak to nine games. Tatis scored on Hosmer’s two-out single to center.